The two most common drop-on-demand inkjet printers use inkjet printheads categorized according to one of two mechanisms of drop formation. Thermal bubble inkjet printers use thermal inkjet (TIJ) printheads with heating element actuators that vaporize ink (or other fluid) inside ink-filled chambers to create bubbles that force ink droplets out of the printhead nozzles. Piezoelectric inkjet printers use piezoelectric inkjet (PIJ) printheads with piezoelectric ceramic actuators that change shape to generate pressure pulses inside ink-filled chambers to force droplets of ink (or other fluid) out of the printhead nozzles.
Piezoelectric inkjet printheads are favored over thermal inkjet printheads when using jettable fluids whose higher viscosity and/or chemical composition prohibit the use of thermal inkjet printheads, such as UV curable printing inks. Thermal inkjet printheads are limited to jettable fluids whose formulations can withstand boiling temperature without experiencing mechanical or chemical degradation. Because piezoelectric printheads use electromechanical displacement (not steam bubbles) to create pressure that forces ink droplets out of nozzles, piezoelectric printheads can accommodate a wider selection of jettable materials. Accordingly, piezoelectric printheads are utilized to print on a wider variety of media.
Piezoelectric inkjet printheads are commonly formed of multilayer stacks. Ongoing efforts to improve piezoelectric inkjet printheads involve reducing fabrication and material costs of each layer in the stacks while improving the printheads' performance, size and robustness.